This invention relates generally to pumps and, more particularly, to a thermal relief valve for pumps for fluids such as water, ethylene glycol, aqueous firefighting foam fluid, or the like.
During the operation of some types of pumps, it is possible that the temperature of the pump fluid will be caused to rise to a temperature which is too hot for the safe operation of the pump. This would occur, for example, when a pump operator closes the discharge lines of the pump and allows the pump to operate for too long a period of time in a "dead head" condition. This could result in damage to the pump and injury to the pump operator as a result of the fluid temperature becoming too hot for safe operation.
It is the general object of the invention to provide a thermal relief valve for pumps which will operate to open and discharge fluid from the pump when an excessive temperature of the pump fluid is sensed. The thermal relief valve of the invention protects the pump from damage and the operator from injury by allowing the hot fluid to be discharged from the pump automatically when the pump fluid rises to an excessive temperature condition. This fluid discharge prevents the overheating of the pump fluid that could cause the pump fluid to boil and the pump pressure to rise beyond a critical limit. When the thermal relief valve of the invention causes the hot fluid to be discharged from the pump, cool fluid is drawn into the pump by way of the pump suction or inlet whereby the temperature of the pump fluid will stabilize at a safe temperature controlled by temperature sensing means of the thermal relief valve.
Briefly stated, the thermal relief valve in accordance with the invention is adapted to sense the fluid temperature of the pump and to open when this fluid temperature becomes too high and discharge the hot fluid from the pump. The thermal relief valve comprises a valve body which defines a flow control chamber and has an inlet for delivering fluid from the pump to the flow control chamber. There is also provided a relief passage means in the valve body for the flow of fluid from the flow control chamber to discharge and seal means at the upstream end of the relief passage means. The thermal relief valve of the invention also comprises a control means cooperable with the seal means to block flow therepast in a first control position and to permit flow therepast to the relief passage (and discharge) in a second control position. There is also provided a temperature responsive means for actuating the control means between said first and second control positions, the temperature responsive means including a temperature sensing means contained within the valve body and having an actuating member mounted for movement through an actuating movement in response to the sensing of a temperature increase by the temperature sensing means. The elements of the thermal relief valve are constructed and arranged so that the control means is operatively connected to the temperature responsive means to be movable between its first and second control positions in response to the movement of the actuating member through its actuating movement to thereby discharge pump water when an elevated temperature condition is sensed.
In accordance with another feature of the invention, there is provided a control means in the form of a piston which is movable within a cylinder chamber and is designed to have a pressure balance across the upstream and downstream sides thereof whereby the thermal relief valve can be actuated between its control positions by a minimum of actuating force.
In accordance with another feature of the invention, the design of the elements of the thermal relief valve are compact and such that the valve can be mounted directly into the pump body or in any piping system by threaded engagement thereof.
In accordance with another feature of the invention, the temperature sensing means comprises a wax element actuator.
The above and other objects and features of the invention will become apparent from the following detailed description.